In uart_cpu_getdev_console() when determinig whether we should use a serial console anyway because input-device is set to keyboard and output-device is set to screen but no keyboard is plugged in don't assume that a device node for the input-device alias exists. While this is true for RS232 keyboards (the node of the SCC and UART respectively which controls the keyboard doesn't disappear when no keyboard is plugged in) this assumption breaks for USB keyboards. It's most likely also not true for PS/2 keyboards but OFW doesn't reliably switch to a serial console when the potential keyboard is a PS/2 one which isn't plugged in so this couldn't be verified properly.
In uart_cpu_getdev_console() when determinig whether we should use
a serial console anyway because input-device is set to keyboard and
output-device is set to screen but no keyboard is plugged in don't
assume that a device node for the input-device alias exists. While
this is true for RS232 keyboards (the node of the SCC and UART
respectively which controls the keyboard doesn't disappear when no
keyboard is plugged in) this assumption breaks for USB keyboards.
It's most likely also not true for PS/2 keyboards but OFW doesn't
reliably switch to a serial console when the potential keyboard is
a PS/2 one which isn't plugged in so this couldn't be verified
properly.

Reported by:	Will Andrews <will@csociety.org>, obrien
MFC after:	1 week

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase